An array of Zymoseptoria tritici effectors suppress plant immune responses
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Abstract
Zymoseptoria tritici is the most economically significant fungal pathogen of wheat in Europe. However, despite the importance of this pathogen, the molecular interactions between pathogen and host during infection are not well understood. Herein, we describe the use of two libraries of cloned Z. tritici effectors that were screened to identify effector candidates with putative pathogen associated molecular pattern (PAMP) triggered immunity (PTI)-suppressing activity. The effectors from each library were transiently expressed in Nicotiana benthamiana , and expressing leaves were treated with bacterial or fungal PAMPs to assess the effectors’ ability to suppress reactive oxygen species (ROS) production. From these screens, numerous effectors were identified with PTI-suppressing activity. In addition, some effectors were able to suppress cell death responses induced by other Z. tritici secreted proteins. We used structural prediction tools to predict the putative structures of all of the Z. tritici effectors, and used these predictions to examine whether there was enrichment of specific structural signatures among the PTI-suppressing effectors. From among the libraries, multiple members of the killer protein-like 4 (KP4) and killer protein-like 6 (KP6) effector families were identified as PTI-suppressors. This observation is intriguing, as these protein families were previously associated with antimicrobial activity rather than virulence or host manipulation. This data provides mechanistic insight into immune suppression by Z. tritici during infection, and suggests that similar to biotrophic pathogens, this fungus relies on a battery of secreted effectors to suppress host immunity during early phases of colonisation.
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This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at https://prereview.org/reviews/12802561.
Within this study, Thynne et al. screen two libraries of Zymoseptoria effectors for suppression of elicitor-induced ROS and cell death. Through this approach they identify promising effector candidates for future investigation. Interestingly, they highlight that some of these identified effectors share structural homology. However, we have highlighted some issues with the clarity of the manuscript, as well as lack of cohesion between the two experimental datasets. Notably, we would have liked to see a more cohesive nomenclature system used for the effector names.
Due to the variation within the data collection methods of both libraries, some aspects of the manuscript were harder to follow. …
This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at https://prereview.org/reviews/12802561.
Within this study, Thynne et al. screen two libraries of Zymoseptoria effectors for suppression of elicitor-induced ROS and cell death. Through this approach they identify promising effector candidates for future investigation. Interestingly, they highlight that some of these identified effectors share structural homology. However, we have highlighted some issues with the clarity of the manuscript, as well as lack of cohesion between the two experimental datasets. Notably, we would have liked to see a more cohesive nomenclature system used for the effector names.
Due to the variation within the data collection methods of both libraries, some aspects of the manuscript were harder to follow. We would appreciate seeing some attempt of integrating these libraries, which would make following some of the analyses clearer. Furthermore, the manuscript doesn't explicitly specify whether signal peptides are included when expressing these effectors in-planta. We believe the apoplast or cytoplasmic localisation of the effectors is a significant characteristic to include within the manuscript.
We've grouped comments by figure and table below.
Table 1:
- The font is too small.
- Could explicitly state which DPI values are symptomless and necrotrophic.
- A continuous colour scale would be better, rather than the binary dark/light green used.
Figure 1:
- There is no explanation of the different dot-points (larger black and smaller grey). This should be within the figure legend.
- The smaller grey points are not well visualised, they could be bigger or a different colour.
- There is a lack of explanation surrounding replicates used (technical and biological) within the legend.
- There is no explanation of what the structural groups correspond to.
Table 2:
- There is a lack of clarity of possible overlap between the effectors in Table 1 and Table 2.
Figure 2:
- This figure seems to be presenting very similar data to Figure 1, but in a different format. We would like to highlight how Figure 1 data is normalised, but Figure 2 is not.
Figure 3:
- This figure needs a level of quantification; we would suggest either the level of suppression observed or frequency of presence/absence (including replication data).
Figure 4:
- In section A, what does the asterisk or asterisks represent? This is not explained in the legend, and we cannot find it in-text.
- We would like to see some sort of confidence scoring within the figure or legend for the structural predictions. While pTM values are within the supplementary material, this should be seen within the manuscript as well.
Overall, the idea of the study is straightforward and logical with interesting results for further study. However, we do feel that there was a lack of narrative cohesion, partly due to the datasets being so separate.
Competing interests
The authors declare that they have no competing interests.
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